Enter the room in ball mode and let the hoppers jump against the wall a couple of times. Between hops, unmorph and shoot the lower hopper.

Entrance condition:

{
  "comeInNormally": {}
}

Requires:

"Morph"
"canPrepareForNextRoom"
{
  "enemyKill": {
    "enemies": [
      [
        "Blue Sidehopper",
        "Blue Sidehopper"
      ]
    ]
  }
}

Clears obstacles: A

Unlocks doors:

{"types":["ammo"],"requires":[]}

Dev note: The ceiling hopper can be moved off camera instead of killed, but there's not an obstacle to represent that yet.